This invention relates in particular to the construction of mining planers and in particular to a new and useful drive for a planer having a sprocket chain.
The invention relates particularly to a planer drive with a sprocket wheel for a planing chain and a driveshaft for the sprocket wheel, the sprocket wheel having a secondary chain ring and the driveshaft a primary chain ring and forming a friction clutch. The secondary chain ring has a revolving, conical, annular groove associated with the primary chain ring and the primary chain ring has radial holes distributed over its circumference and associated with an annular groove for the accommodation of clutch pins. Conical pin heads of the clutch pins are wedgeable in the annular groove, for which purpose a freely mounted centering ring with a wedge surface working against the pin bases is axially/radially adjustable in the primary chain ring by means of a pressure ring. The conical pin heads are designed as friction segments attached to the clutch pins.
A similar planer drive is known, in which the friction clutch or its clutch elements are already characterized by low wear because different materials are used both for the clutch pins and for the conical pin heads. While the strength characteristics are of major importance for the clutch pins, the friction coefficients and the wear characteristics are of primary importance for the conical pin heads. In addition, soft engagment and uniform absorption of power peaks to prevent overloads are achieved.
The invention provides a planer drive whose friction clutch is characterized by reduced specific contact pressure and assures that friction heat, resulting from slippages when engaging, is dissipated unobjectionably.
In such a planer drive the invention solves this problem in that the primary chain ring has radial holes for the clutch pins on at least two circles juxtaposed at a predetermined distance and the friction segments attached to the clutch pins form two revolving friction rings whose outer flanks work against the annular groove flanks, and in that the secondary chain ring has, at least on one circle located in projection between the two circles on the primary side, a friction ring immersing centrally between the two friction rings on the primary side, and working with an appropriate amount of tape against the inner flanks of the rings. The friction ring on the secondary side is mounted so as to be axially movable in the annular groove. The consequence of these measures of the invention is that the friction rings, mutually engaging alternately, form a disc clutch in which the central friction ring, due to its axial mobility, always assures perfect compensation of wear on the friction rings, even when not uniform. The taper of the mutually engaging friction rings contributes to this also so that the flank contact is always perfect. Since the friction area is considerably enlarged due to the mutually engaging friction rings, a considerable reduction of the specific contact pressure is also achieved, and the friction heat caused by slippage can be dissipated through large areas. This virtually prevents "seizing" of the friction rings, and the so-called emergency operating characteristics are maintained at all times, because an oil film forming between the friction surfaces of the friction rings does not break down on account of the low specific contact pressures. The clutch pins are also stressed considerably less because of the lower specific contact pressures. While the friction clutch of the known planer drive, having one friction ring, can be used only up to 200 kW, possibly 250 kW motor capacity, the friction clutch according to the invention is suited for motor capacities up to more than 300 kW. Soft engagement and reduced wear are always assured. The essential advantages obtained by the invention are seen therein.
Other significant features of the invention are enumerated below. One independently significant suggestion of the invention provides for the secondary chain ring to have, distributed over its circumference, on a circle coaxial to the friction ring on the secondary side, radial holes to accommodate clutch pins with conical friction segments forming the secondary friction ring. A particularly flexible adaptation of the central friction ring to the two outer friction rings which are radially movable towards the central friction ring via the wedge surface of the centering ring is achieved in this manner. The friction segments of the friction rings on the primary side may be mutually staggered in accordance with the sprocket wheel gaps so as to avoid, with certainty, canting between the friction segments of the central friction ring and the two outer friction rings. For, the central friction ring or the friction ring on the secondary side is preferably divided into three or four friction segments, with each of which are associated several clutch pins fixed in their radial holes. These clutch pins serve the purpose of fixing the friction segments of the secondary friction ring in circumferential directions while not impairing their axial mobility. For exial mobility, the secondary chain ring has an appropriately wide, revolving, channel-like bearing recess in the annular groove area, which recess is engaged by the secondary clutch pins and friction segments in the area of the segment base.
Accordingly, it is an object of the invention to provide an improved drive for a planer wherein a clutching engagement is effected between the drive shaft and a sprocket chain ring through radially extending pins having friction pinheads which are adjustably engaged against the flank of a revolving groove of the sprocket wheel.
A further object of the invention is to provide a drive which is simple in design, rugged in construction and economical to manufacuture.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.